A street in the Cuban capital, Havana, is home to 12 sets of twins, ranging from toddlers to senior citizens. Some say it could be something in the water. Others point to a tree with mystical significance for locals. And maybe it's just chance. Photo: In this September 29, 2013 photo, nine-year-old twin sisters Camila, left, and Carla Rodriguez pose for a portrait along their street in Havana, Cuba. 12 sets of twins live along two consecutive blocks in western Havana, ranging in age from newborns to senior citizens. “We love living on this block because we have twin friends”, said Carla. (Photo by Ramon Espinosa/AP Photo)

Kenichi Ito runs on his arms and legs on a race course on his way to setting the Guinness World Record fastest time for the 100-meter dash on all fours at Komazawa Olympic Park Stadium in Tokyo Thursday, November 14, 2013. The 30-year-old Japanese finished in 16.87 seconds Thursday, shaving more than half a second off his 2012 run of 17.47. (Photo by Shizuo Kambayashi/AP Photo)

A model poses with “The Wellbeing Toilet” the winning entry from a Dyno-Rod Initiative to create a new design for the domestic toilet at Central Saint Martins on November 18, 2013 in London, England. The concept was commissioned to mark 50 years of Dyno-Rod and World Toilet Day on November 19th, 2013 The “Wellbeing Toilet” looks at the health and wellbeing aspect of getting rid of your bodily waste by being sculpted to enhance the position of your body by enabling you to squat rather than sit. (Photo by Miles Willis/Getty Images for Dyno-Rod)

Olive Ridley turtle hatchlings (Lepidochelys olivacea) sit in baskets and trays at the turtle camp La Gloria, before their release into the ocean in Tomatlan November 15, 2013. Twenty years ago, Mexico's government implemented ecological plans to protect the sea turtles from being hunted for their leather and meat and established conservation areas and a pay system for local residents to protect turtle nests. Millions of baby turtles hatch on the shores in November and December, according to an environmental group. It is estimated that in 2012, there were 20 million newborns. Hatching season is still underway, but officials say they expect there will be even more turtles born this year. (Photo by Alejandro Acosta/Reuters)

Female indigenous players vie for the ball during the final match of Peladao, the amateur football tournament, in Manaus, Amazonas state, Brazil, on November 24, 2013. Peladao is known as the biggest amateur football tournament in the world, with more than 1000 teams competing in various categories since 1973. The indigenous category was created in 2005 and eight teams participated this year. (Photo by Yasuyoshi Chiba/AFP Photo)

Nine year old girl Barsati reacts while walking on a tightrope in Mumbai on February 11, 2014. Barsati, and her younger brother Rajababu, (4) earn an average of around 2000 rupees (32 dollars) per day from pedestrians and tourists performing various acts on the tightrope near the city's iconic landmark Gateway of India. (Photo by Indranil Mukherjee/AFP Photo)

A police officer sprinkles colored powder onto a police dog at Nepal's Central Police Dog Training School during a dog worship day as part of the Diwali festival, also known as Tihar Festival, in Kathmandu, Nepal, 10 November 2015. The Tihar festival is the second major festival for Nepalese Hindus and this year is held from 10 November 2015. (Photo by Narendra Shrestha/EPA)

Revellers in fancy dress enjoy the atmosphere during the British Fancy Dress Day on November 12, 2015 in Benidorm, Spain. The British Fancy Dress Day is one of the biggest fancy dress parties in Europe and is held the day after the Benidorm fiestas in November. The tradition started over 20 years ago when Manolo from Sinatras Club offered a free drink to anyone who dress up. Nowadays around 30,000 people, mostly British Expats living in Spain and tourists visiting the Costa Blanca resorts, attends, attend the event. (Photo by David Ramos/Getty Images)